At head of title: University of Florida, Cooperative Extension Service, Institute of Food and Agricultural Sciences, EDIS.

General Note:

"This document is HS-808, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date July 2001."--Footnote.

Pepper mild mottle virus (PMMoV) oc-
curs worldwide in field-grown bell, hot and or-
namental pepper species. It has also been
found in greenhouses in pepper cultivars in
Canada and Spain where greenhouse produc-
tion practices are ideal for rapid spread of the
disease. PMMoV has been identified in com-
mercial bell pepper fields in Florida, in South-
west Florida in January 2000 and then in South-
east Florida in December 2000. Disease inci-
dence (the percentage of plants infected) of up
to 30% was estimated in the Florida outbreaks.
Because foliar symptoms can be mild, infected
plants may not be noticed until the fruit symp-
toms are evident, resulting in spread to neigh-
boring plants and higher yield losses.

Causal agent and symptoms

PMMoV is in the tobacco mosaic virus
(tobamovirus) family. It is spread by mechani-
cal transmission and by infected seed but can-
not be transmitted by insects. The virus is iden-
tified by the symptoms it causes on indicator
host plants, serological methods such as ELISA
and the morphology of inclusion bodies in-
duced by the virus in host plant cells. A repu-
table laboratory should be used to ensure ac-
curate identification of the virus.

Symptoms caused by PMMoV on pep-
per plants may vary between cultivars. Infected
leaves are frequently puckered and mottled
yellow or light green (Figure 1). Leaf symptoms
are more evident on younger leaves. Plants
can be stunted, especially when the infection
occurs early in the plant's development (Fig-
ure 2). Although infected fruit can be some-
what reduced in size and show variations in
color (mottling and color changes at maturity),
the most obvious symptom is the distorted or
lumpy appearance of the fruit (Figure 3). Older
fruit may develop brown streaks or splotches.

Most cultivars and species of pepper
(genus Capsicum) are susceptible to PMMoV.
However, this virus does not affect tomato, egg-
plant or tobacco, which are in the same family
(Solanaceae).

Control

Avoidance is the best means of control.
Only seed tested and determined to be free of
virus should be planted. Infected seed can be
treated with heat, acid, or trisodium phosphate
but virus both on the seed surface and inside
the seed must be removed to ensure freedom
from disease. Seed treatments can reduce seed
germination even if done correctly. Although
a gene for resistance has been identified, there
are very few resistant field cultivars available
in the US.

PP-55

The virus enters the plant through mi-
croscopic abrasions or wounds. There are no
chemical or biological control methods that can
be used to control the disease once the plant is
infected. The virus in association with plant
sap can be present on skin, clothing, tools and
equipment so infected plants should be
handled as little as possible and infected fields
should be staked, tied, harvested, sprayed, last
to avoid spreading the virus to uninfected ar-
eas. Infected plants should be removed if elimi-
nation can be done without contact with healthy
plants. A symptomless plant on either side of
those removed should also be rogued, as it is
likely that they are also infected. Some viruses
can be spread through smoke so diseased
plants should be disposed of by composting
or burying rather than by burning.

Viruses in the tobacco mosaic virus fam-
ily are notoriously easy to spread and difficult
to eliminate. To reduce spread of the disease,
anyone working with the plants should wash
their hands with 70% alcohol or strong soap,
also cleaning under the nails. Clothing should
be washed as frequently as possible. Equip-
ment should be washed then cleaned with 3%
trisodium phosphate and not rinsed. Stakes
from infected areas of the field should be dis-
carded or soaked in 3% trisodium phosphate
before being reused. Household bleach can also
be used to clean equipment or stakes.

Diseased plant material will remain in-
fectious until completely broken down. Till-
age, increased irrigation and high temperatures
encourage the breakdown of plant material in
the soil. Any infected plant material in the soil
can serve as a source of inoculum for subse-
quent crops so crop rotation should be prac-

ticed, if possible. Volunteer peppers and
weeds, particularly those in the Solanaceae fam-
ily (such as nightshades), should be removed
to reduce possible sources of infections.
Accurate identification is important to
avoid yield loss. Other pepper viruses can have
similar symptoms but may be spread and con-
trolled through different means. For example,
pepper mottle virus, which has somewhat simi-
lar symptoms and is also found in Florida, is
transmitted by aphids and not by mechanical
means. Check with a laboratory that does vi-
rus testing, or with your local Cooperative Ex-
tension office for identification.